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Disheswith
Wide Band Single Pixel FeedsP. Dewdney
WP2 meetingOct 18, 2011
Wideband Single‐Pixel Feeds(WBSPF): Contributors• US TDP funded investigations
• Several different feeds designed and investigated• German Cortez (Cornell University)• Sandy Weinreb (Caltech)• Bill Imbriale (JPL)• Jack Welch, Dave de Boer, et al (ATA)
• Chalmers University • Miroslav Pantaleev, Per‐Simon Kildal, et al.• Long heritage of work on wide band feeds• Collaborated with TDP• On‐going investigation on Eleven Feed
• Herzberg Institute (NRC Canada) & U. Victoria• Log‐periodic log‐spiral• Stephane Claude, Jens Bornemann, et al
WBSPF: Definition
• SKA Baseline design: corrugated horn feeds • Bandwidth ratios ~2:1
• Feeds with bandwidth ratios approaching >>2:1.
WBSPF Options
• A Quad‐ridged feed design being developed at Cal Tech• Improvement of the Lindgren feed sold by ETS‐Lindgren
• QSC feed• Measured input match better that ‐10 dB over 10:1 bandwidth.
• ATA feed• Ultra‐wide band log‐periodic feed developed for the Allen Telescope Array• High gain• Frequency coverage in excess of 15:1• Measured performance
• The Eleven feed • Compact feed based on a parallel folded dipole configuration over a ground plane.• Measured data.
• Directional Log Periodic Log Spiral Antenna • University of Victoria & HIA, Canada.
Eleven Feeds (Chalmers)
• On‐going work at Chalmers University on this feed.• Emphasis on compact, coolable feed to operate from 1.2 –10 GHz (folded design).• By reducing bandwidth ratio to 4:1, try to approach the performance of a corrugated horn.
WBSPF: Comments
•WBSPF Advantages for SKA:• Potentially lower total system cost than multiple corrugated horns• instantaneous bandwidth coverage is much greater
• Disadvantages• No clear science requirement for instantaneous wide band (10:1) coverage has been identified.
• Note: on a single dish a WBSPF may have an advantage• A/T of dishes typically lower (see following slides).• Large instantaneous bandwidth to be sent & processed:
• would be required only if the entire band is transmitted.• Other issues:
• Most (not all) WBSPFs require wide opening‐angle optics (low gain), whereas horn feeds tend to be higher gain.• In offset design, this can be altered by adjusting the sub‐reflector.
Wide Band Single Pixel Feeds considered
QSC Feed
ATA FeedLindgren Feed
Eleven Feed
Wide Band Single Pixel Feeds considered
Ring Loaded Corrugated Horns:15‐m Offset Gregorian
From Cortez et al.
Ring Loaded Corrugated Horns:15‐m Offset Gregorian
7.0 m2/K
From Cortez et al.
Quad Ridge:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
Eleven Feed:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
QSC‐i Feed:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
ATA:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
Log Periodic‐Log Spiral:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
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